1. Field of the Invention
The present disclosure relates to a switching mechanism for a gas insulated switchgear, and particularly, to a switching mechanism for a gas insulated switchgear, which can reduce the size of an actuator as a driving energy source and reduce the overall size of the gas insulated switchgear by including a spring for charging elastic energy when it moves to a contacting position and discharging elastic energy when it moves to a separating position.
2. Background of the Invention
In general, a gas insulated switchgear is electric power equipment which is installed on an electric power transmission line or an electric power distribution line of ultra-high voltage electric power greater than several tens of kilovolts, for example, at a power plant or substation.
The gas insulated switchgear may internally include a switching mechanism having a breaking position (that is the separating position) for breaking a circuit in the event of a fault current such as a ground fault or electric shortage and a closing position (also referred to as the contacting position) for applying electric current to the circuit at normal times.
The gas insulated switchgear of this type is also referred to as a gas insulated breaker. The switching mechanism is also referred to as an arc extinguishing mechanism because it extinguishes arc by blowing an insulating gas to a contact when the circuit is broken.
The present invention relates to such a switching mechanism for a gas insulated switchgear.
The configuration and operation of the switching mechanism for the gas insulated switchgear according to the related art will be described with reference to FIGS. 1 and 2.
The switching mechanism for the gas insulated switchgear according to the related art can be generally divided into a stationary contactor 1 and 1a and a movable contact section 30, 10, and 40.
The stationary contactor 1 and 1a includes a stationary arc contactor portion 1a at the center and a stationary main contactor portion 1 provided to surround the stationary arc contactor portion 1a. 
The movable contact section 30, 10, and 40 includes a stationary cylinder 10 which is hollow inside and opened at both longitudinal ends and a movable contactor portion 30 which penetrates the stationary cylinder 10 and is linearly movable.
Further, the movable contactor portion 30 includes a movable main contactor 20, a cylinder rod 31, a movable arc contactor 32, an auxiliary nozzle 33, and a main nozzle 34.
The movable contact section 30, 10, and 40 may further include a connecting rod 40 having one end to be connected to the cylinder rod 31 and the other end to be connected to a driving source (not shown) such as a spring actuator.
The movable main contactor 20 is a contactor which is linearly movable to a contacting position for contacting the stationary main contactor portion 1 or a separating position for separating from the stationary main contactor portion 1.
The movable main contactor 20 is formed further behind the movable arc contactor 32. Hence, when moving to the contacting position, the movable main contactor 20 comes in contact with the stationary contactor 1 and 1a later than the movable arc contactor 32 does, and when moving to the separating position, the movable main contactor 20 is separated from the stationary contactor 1 and 1a earlier than the movable arc contactor 32 is.
The movable main contactor 20 is connected to the movable arc contactor 32 via a piston (given no reference numeral) and linearly moves in the same direction as the linear motion of the movable arc contactor 32.
The movable arc contactor 32 is connected to the front end of the cylinder rod 31, and linearly moves to the contacting position or the separating position according to the linear motion of the cylinder rod 31.
An insulating gas compression chamber is formed by the inside of the stationary cylinder 10 and the piston, and the compression chamber communicates with internal spaces of the movable arc contactor 32, main nozzle 34, and auxiliary nozzle 33 through the cylinder rod 31.
The cylinder rod 31 is a rod which is driven and connected to the movable main contactor 20 and the movable arc contactor 32 to provide a driving power for linear motion to the movable main contactor 20 and the movable arc contactor 32.
The cylinder rod 31 is formed like an elongate cylinder being hollow inside and has a gas communication opening (not shown) which communicates with the compression chamber.
The driving power of the cylinder rod 31 is obtained from the connecting rod 40 which is connected to a driving source such as a spring actuator.
The movable arc contactor 32 is a contactor which is linearly movable to the contacting position for contacting the stationary arc contactor portion 1a or the separating position for separating from the stationary arc contactor portion 1a. 
The movable arc contactor 32 protrudes further forward than the movable main contactor 20. Hence, when moving to the contacting position, the movable arc contactor 32 comes in contact with the stationary contactor 1 and 1a earlier than the movable main contactor 20 does, and when moving to the separating position, the movable arc contactor 32 is separated from the stationary contactor 1 and 1a later than the movable main contactor 20.
The main nozzle 34 is attached to a front end portion of the movable main contactor 20 by an attachment method, e.g., welding, and ejects compressed arc extinguishing gas toward the stationary arc contactor portion 1a so as to extinguish the arc produced when the movable arc contactor 32 is separated from the stationary arc contactor portion 1a. 
The auxiliary nozzle 33 is attached to the movable arc contactor 32 by an attachment method, e.g., welding, so as to protrude further forward than the movable arc contactor 32, and ejects the compressed arc extinguishing gas in the compression chamber toward the main nozzle 34 so as to extinguish the arc produced when the movable arc contactor 32 is separated from the stationary arc contactor portion 1a. 
The operation of the switching mechanism for the gas insulated switch according to the related art will be described with reference to FIGS. 1 and 2.
First of all, the movement of the switching mechanism from the separating position shown in FIG. 2 to the contacting position shown in FIG. 1 will be described.
The connecting rod 40 connected to a driving energy source (not shown) such as a spring actuator linearly moves from the separating position shown in FIG. 2 in the direction of arrow a of FIG. 1 by driving power from the driving energy source.
Then, the cylinder rod 31 connected to one end of the connecting rod 40 linearly moves in the direction of arrow a, and the movable arc contactor 32 connected to the front end of the cylinder rod 31 also linearly moves in the direction of arrow a.
Therefore, the movable main contactor 20 connected to the movable arc contactor 32 via the piston also linearly moves in the direction of arrow a.
Hereupon, the movable arc contactor 32 comes in contact with the corresponding stationary arc contactor portion 1a, and the movable main contactor 20 comes in contact with the corresponding stationary main contactor portion 1, thereby completing the movement to the contacting position as shown in FIG. 1.
The movement of the switching mechanism from the contacting position shown in FIG. 1 to the separating position shown in FIG. 2 is performed in a direction opposite to that of the above-described movement.
That is, the connecting rod 40 connected to the driving energy source (not shown) such as the spring actuator, linearly moves from the contacting position shown in FIG. 1 in the direction of arrow b of FIG. 2 by the driving power from the driving energy source.
Then, the cylinder rod 31 connected to one end of the connecting rod 40 linearly moves in the direction of arrow b, and the movable arc contactor 32 connected to the front end of the cylinder rod 31 also linearly moves in the direction of arrow b.
Therefore, the movable main contactor 20 connected to the movable arc contactor 32 via the piston also linearly moves in the direction of arrow b.
Hereupon, the movable arc contactor 32 is separated first from the corresponding stationary arc contactor portion 1a. At this time, no arc is generated because the movable arc contactor 32 is still in contact with the corresponding stationary arc contactor portion 1a. Subsequently, the movable arc contactor 32 is separated from the corresponding stationary arc contactor portion 1a. At this time, the arc extinguishing gas compressed in the compression chamber is ejected toward the stationary arc contactor portion 1a via the auxiliary nozzle 33 and the main nozzle 34, thereby rapidly extinguishing the arc. As such, the movement to the separating position as shown in FIG. 2 is completed.
The above-described switching mechanism for the gas insulated switchgear according to the related art receives driving energy from the spring actuator as the driving energy source in order to move to the contacting position or the separating position.
The spring actuator may be a closing spring for providing the driving energy to the contacting position and a trip spring (also referred to as an opening spring) for providing the driving energy to the separating position.
As used herein, the closing spring provides not only energy for driving the above-described switching mechanism to the contacting position, but also energy for compressing the trip spring so as to charge elastic energy for driving the switching mechanism to the separating position.
Accordingly, the elastic energy provided by the closing spring is required to be 1.5 to 2 times larger than the elastic energy provided by the trip spring.
Generally, a gas insulated switchgear can be used for longer than 20 years, during which the switching mechanism performs a lot of opening and closing operations. Thus, the switching mechanism for the gas insulated switchgear according to the related art requires high elastic energy provided by the closing spring, and therefore suffers mechanical damage and durability decrease, resulting in a decrease in the operational reliability of the switching mechanism.